Thermostat



F. W. ROBERTSHAW.

THERMOSTAT.

APPLICATION FILED JUNE 3,1920.

1,387,61 8, 1 I Patented Aug. 16, 1921.

gwvenioz and FREDERICK W. BOIBERTSHAW, OF PITTSBURGH, PENNSYLVANIA.

THERMOSTAT.

Application filed June a, 1920. Serial No.

To all 7.0720771 it may concern:

' Be it known'that I, FREDERICK 'W. Rom ERTSHAW, a citizen of the United States, residing at Pittsburgh, Allegheny county, Pennsylvania, have invented a new and useful Improvement in Thermostats, of which the following is a full, clear, and exact desc ription,:reference being had to the accompanying drawings, in which igure 1 is a longitudinal sectional view of a thermostat embodying my invention;

Fig. 2 is a section on the line 11-11 of and more particularly to thermostats of the the carbon does I have discovered that this disintegration general characterdescribed and claimed in my Patent No. 864,263, 1907. In that thermostatv the movable element consists of a rod of compressed carbonaceous inaterialincased by a tubing usually of iron, steel, While the thermostats of my said patent have been highly-successful in practice, and have been used to a large extent, it is found that the carbon rod, when made of some grade of material, or with certain binding .when subjected to high temperatures the carbon rod tends to disintegrate. Apparently, the cause for this disintegration is that the material of the rod has a greater ailinity for oxygen than has the metal of the casing; and that when the parts are heated, the carbon rod absorbs oxygen from the casing. However this may be, the fact remains that from some cause this disintegration of occur.

Specification of Letters Patent.

dated August 27th,

or other ferrous alloy.'

Patented Aug. 16', 1921. 386,218.

can be largely prevented, and the life of the carbon element of the thermostat greatly extended, if a suitable protector is placed around the carbon and between it and the casing. For this purpose I have obtained excellent results by the use of a protector consisting of a tubing of copper. Referring to the accompanying drawings 1n which I have illustrated one embodiment of my invention, the numeral 2' designates the rod of compressed carbonaceous mate ma], 3 the outer casing and 4 the interposed copper protector. 5 designates any suittable device upon which the rod 2 is arranged 0 act.

The advantages of my invention result from the provlsion of a protector placed around the carbon rod and between it and 1ts casing which acts to greatly increase the life and effectiveness of the said rod.

claim;

1. A thermostat comprisin pansible element composed 0? carbon, an outer metal casing for the same, and a protective cove1'ing of copper interposed between the rod and the casing, substantially as described.

2. A thermostat comprising a non-expansible element consisting of a carbon rod, an expansible metal element surrounding said rod, and a-protective covering for said rod interposed between the said elements, said covering consisting of a metal which will prevent chemical reaction between said elements, substantially as described.

In testimony whereof, I have hereunto set my hand.

FREDERICK W; ROBERTSHAW.

a non-ex- 

